Flow injection analysis of ethyl xanthate by in-line dialysis and UV spectrophotometric detection

A simple and sensitive spectrophotometric flow method for determination of low concentrations of the flotation collector O-ethyldithiocarbonate (ethyl xanthate, CH₃CH₂-O-CS₂⁻) in solutions is described. The method is based on ethyl xanthate detection at 301 nm in medium of NaOH 50 mmol L⁻¹. By injection of 200 μL of sample, the analytical method shows linear response for the ethyl xanthate concentration from 0.5 up to 500 μmol L⁻¹. Successive injections of 4 μmol L⁻¹ ethyl xanthate (n = 23) show a coefficient of variation lower than 0.6%, denoting high repeatability. The detection limit is 0.3 μmol L⁻¹. At a flow rate of 2.0 mL min⁻¹, a frequency of 120 injections/h of ethyl xanthate can be attained. By introduction of a tangential dialysis cell in the FIA system, the manual sample filtration step with 0.22 μm filter was eliminated and the residual interference of suspended material, was completely overcome even for unfiltered sludge suspension samples, an important advantage that compensates for the frequency reduction to 25 injections/h elevation and detection limit elevation to 2 μmol L⁻¹, still outreaching for many applications. Potential applications of the method embrace the at line determination of ethyl xanthate in the ore processing industry, control of the concentration at its optimal level during the flotation process, as well as monitoring of residues in the effluents.     

An intelligent flow analyser for the in-line concentration, speciation and monitoring of metals at trace levels

An intelligent and versatile flow system is proposed for the in-line speciation and/or concentration of metal ions at a wide range of concentrations without requiring manifold reconfiguration. On one hand, sample enrichment strategies are accomplished using packed-bed reactors, on the other hand speciation procedures are readily performed exploiting the selective complexation of the different oxidation states with the appropriate chromogenic reagents.

The potentials of the automated methodology were evaluated using the spectrophotometric monitoring of iron as a model of chemistry. Under the optimised physical and chemical variables, linear analytical curves over the ranges 0.025–0.5 or 2.0–40 mg l⁻¹ Fe were attained. The 3σ detection limit, the repeatability at the 0.5 mg l⁻¹ level, the enrichment factor for a sampling volume of 10 ml, and the maximum injection throughput were 8.4 ng ml⁻¹ Fe, 2.5%, 58.6 and 22 h⁻¹, respectively. The flowing system was applied to the speciation analysis of iron in waters, pharmaceutical formulations and agricultural products, using ICP-OES detection as an external reference method for total iron determination.

A remarkable feature of the expert system hereby presented is the ability to decide by itself if the pre-concentration and/or oxidation of the sample zone is required.     

Determination of trace levels of sulphate in water using flow-injection and in-line preconcentration

Sulphate is preconcentrated on a strong anion-exchange resin and determined using the effect of sulphate ions on the complexation of methylthymol blue and barium. A computer-controlled flow-injection analyser is used to automate the whole procedure. The resin has two functions: it preconcentrates sulphate and also separates sulphate from divalent cations that may interfere in the determination step. The system can handle 30 samples per hour and has a working range from 25 to 1000 μg 1^?1 of sulphate. Lower detection limits can be obtained by changing the preconcentration conditions. The effect of both anionic and cationic interferents was studied.     

流动注射光度法测定盐酸普鲁卡因

在盐酸介质中,利用盐酸普鲁卡因－亚硝酸钠－α萘胺的重氨化－偶合反应,建立了流动注射光度法测定盐酸普鲁卡因的新方法。利用控制加 权形心单纯形优化法选择最佳实验条件,测定的线性范围为0－30μg/mL,该法已用于药物中盐酸普鲁卡因含量的测定。     

吗啡的流动注射分光光度法分析研究

本文建立了吗啡的流动注射分光光度分析法。在优化条件下,线性检测范围为30～700μg/ml,回归方程为h=0.0250+1.74×10~(-3)C,相关系数为0.9999,并用于吗啡样品的分析。回收率为99.9％,相对标准偏差为0.43％,样品分析速度为240次/小时。     

Exploiting monosegmented flow analysis to perform in-line standard additions using a single stock standard solution in spectrophotometric sequential injection procedures

The robustness of sequential injection analysis (SIA) was combined with the monosegmented flow analysis (MSFA) approach, in which there is no dispersion of the reaction zone with carrier, to develop a methodology to perform in-line dilution. This approach allows one to know accurately the dilution of sample and reagent inside the monosegment, without the need for determination of dispersion coefficients. As a consequence, the methodology allowed the mechanization of procedures to perform standard additions and to construct analytical curves using a single stock standard solution, with very simple and conventional computation of the sample concentration. The method was illustrated with experiments using the bromothymol blue (BTB) dye, in which no reactions are involved, as well as with the spectrophotometric methodology for determination of Fe(II) using o-1,10-phenanthroline as chromogenic reagent. The resulting method presented a sampling frequency of 30 analyses per hour and a detection limit of 25 μg l⁻¹.     

Spectrophotometric flow-injection determination of sulphate in soil solutions

A flow-injection procedure for spectrophotometric determination of sulphate in soil solutions is proposed. Samples are directly soaked from the soils under field conditions, in-line filtered through ceramic plates, and preserved with thymol. The method involves reaction with barium dimethylsulphonazo(III) (DMSA) in the presence of dimethylsulphoxide (DMSO) with further measuring the decrease in absorbance at 668 nm. A linear response is observed up to about 5 mgl ⁻¹ SO₄, and detection limit (3σ criterion) is 0.1 mg l⁻¹ SO₄. Only 4.5 μg DMSA is consumed per determination. The system is rugged and baseline drift is not observed during extended operation periods. About 60 samples are injected per hour, and the results are precise (r.s.d. <2%) and in agreement with ion chromatography.     

Flow methodology for methanol determination in biodiesel exploiting membrane-based extraction

A methodology based in flow analysis and membrane-based extraction has been applied to the determination of methanol in biodiesel samples. A hydrophilic membrane was used to perform the liquid-liquid extraction in the system with the organic sample fed to the donor side of the membrane and the methanol transfer to an aqueous acceptor buffer solution. The quantification of the methanol was then achieved in aqueous solution by the combined use of immobilised alcohol oxidase (AOD), soluble peroxidase and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The optimization of parameters such as the type of membrane, the groove volume and configuration of the membrane unit, the appropriate organic solvent, sample injection volume, as well as immobilised packed AOD reactor was performed. Two dynamic analytical working ranges were achieved, up to 0.015% and up to 0.200% (m/m) methanol concentrations, just by changing the volume of acceptor aqueous solution. Detection limits of 0.0002% (m/m) and 0.007% (m/m) methanol were estimated, respectively. The decision limit (CCα) and the detection capacity (CCβ) were 0.206 and 0.211% (m/m), respectively. The developed methodology showed good precision, with a relative standard deviation (R.S.D.) <5.0% (n = 10). Biodiesel samples from different sources were then directly analyzed without any sample pre-treatment. Statistical evaluation showed good compliance, for a 95% confidence level, between the results obtained with the flow system and those furnished by the gas chromatography reference method. The proposed methodology turns out to be more environmental friendly and cost-effective than the reference method.     

非平衡流动注射光度法测定微量亚硝酸根的研究

采用流动注射分析技术,研究了在酸性介质中碱性品红与亚硝酸根的反应,用自制的微机化流动注射分析仪准确控制反应时间,利用非平衡法原理,优化了实验条件,建立了测定微量亚硝酸根的新方法。线性范围为０．０～５．０ｍｇ／Ｌ,分析速度达每小时测定３６次。应用该法直接测定煤矿塌陷湖水、鱼塘水、电厂废水和地下水中的亚硝酸根获得满意结果。     

水杨基荧光酮胶束增敏流动注射分光光度法测定微量锗

本文将锗一水杨基荧光酮一溴化十六烷基三甲基铵胶束五色体系应用于流动注射分析，建立了测定微量锗的快速方法。方法采用单通道流路及合并带流路进行试验。对有关的管路参数及试剂浓度等影响因素进行了探讨。优化的流动注射分析体系对锗的检测灵敏度高、重现性好。方法用于混合成试样及有机锗生物制品中锗的测定，结果满意。     

流动注射—分光光度法测定植物中钼

本文将流动注射分析(FIA)引入Mo-SCN~--RhB三元缔合体系测定痕量Mo。不需萃取,反应迅速,重现性好。0～1.6μg/ml Mo符合比耳定律,检测限0.02μg/ml。用预混线圈R_1可克服Fe~(3+)等元素与SCN~-络合的干扰。测定了植物中Mo,结果满意。     

流动注射分光光度法测定微量镉的研究

研究了在Ｔｒｉｔｏｎ Ｘ－１００存在下,以二溴羧基苯基氮氨基偶氮苯（ＤＢＫＤＡＡ）为显色剂的流动注射分光光度测定微量镉的新方法。用ｐＨ１０．５的硼砂－氢氧化钠缓冲溶液作栽流,ＤＢＫＤＡＡ和Ｔｒｉｔｏｎ Ｘ－１００的混合液作试剂流,采用双道流路,在５２０ｎｍ波长下检测反应生成的红色配合物。方法的线性范围是０～０．８０μｇ／ｍＬ,进样频率为１８０样次／小时,直接应用于工业废水中微量镉的测定,结果满意。     

Nanoparticle-based assays in automated flow systems: A review

Nanoparticles (NPs) exhibit a number of distinctive and entrancing properties that explain their ever increasing application in analytical chemistry, mainly as chemosensors, signaling tags, catalysts, analytical signal enhancers, reactive species generators, analyte recognition and scavenging/separation entities.     

Spectrophotometric Determination of Uranium(VI) with Chlorophosphonazo-mN by Flow Injection Analysis

Abstract

A sensitive and selective spectrophotometric flow injection analysis (FIA) method with chlorophosphonazo-mN has been developed for the determination of uranium(VI) in standard ore samples. Most of interfering ions are effectively eliminated by the masking reagent of diethylenetriaminepentaacetic acid (DTPA). In the U(VI)-chlorophosphonazo-mN system, the maximum absorption wavelength is at 680 nm and Beer's law is obeyed in the range of 1 to 15 μg ml^?1. The correlation coefficient of the calibration curve is 0.9998, the sampling frenquency is 60 h^?1, and the detection limit for uranium(VI) is 0.5 μg ml^?1. The composition of the U(VI)-chlorophosphonazo-nN complex was established to be 1:2 by flow-through spectrophotometric and conventional molar ratios methods.     

饮料、甜橙、药片和尿液中维生素C的流动注射分析——2,6-二氯吲哚酚光度法

流动注射2,6-二氯吲哚酚光度法测定维生素C具有灵敏,快速的特点,检出限为0.5μg/ml,分析速度120样/h,取Vc 40μg/ml时测量的相对标准偏差为±0.5％。测定各类样品中Vc含量获得较好的结果。     

测定驱油体系中碱度的流动注射分光光度法

采用流动注射分析技术，以酸碱指示剂－－间硝基酚溶液作载流，实现了三元复合驱油体系中碱的测定；该法可测定10－600mg/L NaOH(强碱），20－1400mg/L Na2CO3(弱碱）；方法的检出限为0．5mg/L NaOH,1mg/L,Na2CO3；对含量为200mg/L的样品测定6次的相对标准偏差为0.6%(NaOH),0.5%(Na2CO3);测定速率每小时达94个样；该法也适用于其它无机碱、有机碱的测定。     

Determination of Orciprenaline Using a Flow Injection Analysis System with Sequential Potentiometric and Spectrophotometric Detection

Abstract

This work describes an attempt to have a flow injection analysis (FIA) system for Orciprenaline with potentiometric and spectrophotometric detectors working sequentially. The potentiometric detection was performed using an orciprenaline ion-selective electrode made of orciprenaline ion-associate with phosphotungstic acid incorporated in a PVC matrix membrane, followed by sequential spectrophotometric detection of the same sample using the reaction of orciprenaline with phosphomolybdic acid in alkaline medium and measurement at 670 nm using a USB2000 fiber-optic spectrophotometer. The method was applied and validated for the assay of different samples that are 1.0 × 10^?2–1.0 × 10^?7 M orciprenaline, and the recovery values for Alupent® tablets, plasma and urine sample ranged from 99.39–100.93, 99.87–100.57, and 98.83–100.64 respectively for the potentiometric detector and 99.66–100.58, 99.78–100.69 and 99.12–100.92 respectively for the sequential spectrophotometric detector. It was found that using the double detection system compensated for both the unselectivity of the spectrophotometric method and the low detection limit of the potentiometric method (6.3 × 10^?4 M). Although two detectors were used in the measurements, the method is still very simple to design and apply, in addition to being rapid and less expensive than other more sophisticated techniques applied in the literature and can therefore be used for other pharmaceutical compounds as well.     

流动注射分光光度法测定砷的研究

本文采用自行设计制造的氢化物发生及吸收装置,将流动注射技术同氢化物发生分光光度法结合在一起,设计了一种不使用载气的流动注射分析系统并对该系统的测定条件进行了实验研究,实验用HNO_3-AgNO_3-聚乙烯醇-乙醇混合液作吸收液,结果证明该系统具有操作简便,成本低廉,分析速度快(30次/小时),灵敏度高,重现性好及线性范围可调的优点。     

Flow Injection Spectrophotometric Determination of N-Acetylcysteine and Captopril Employing Prussian Blue Generation Reaction

A novel flow injection procedure to determine N-acetylcysteine and captopril in pharmaceutical formulations is proposed. The flow procedure developed was based on oxidation of the analytes by Fe(III) in acidic medium and subsequent reaction of the Fe(II) generated with excess hexacyanoferrate(III) to produce soluble Prussian blue (KFe[Fe(CN)₆]) measured at 700 nm. Detection limits of 1.0 × 10^?5 mol L^?1 and 3.0 × 10^?5 mol L^?1 for N-acetylcysteine and captopril, respectively, were found. The sample throughput was 70 h^?1 for both analytes and the results obtained were in agreement at a 95% confidence level with those obtained using reference methods.     

Zone trapping/merging zones in flow analysis: a novel approach for rapid assays involving relatively slow chemical reactions

A novel strategy for accomplishing zone trapping in flow analysis is proposed. The sample and the reagent solutions are simultaneously inserted into convergent carrier streams and the established zones merge together before reaching the detector, where the most concentrated portion of the entire sample zone is trapped. The main characteristics, potentialities and limitations of the strategy were critically evaluated in relation to an analogous flow system with zone stopping. When applied to the spectrophotometric determination of nitrite in river waters, the main figures of merit were maintained, exception made for the sampling frequency which was calculated as 189 h⁻¹, about 32% higher relatively to the analogous system with zone stopping. The sample inserted volume can be increased up to 1.0 mL without affecting sampling frequency and no problems with pump heating or malfunctions were noted after 8-h operation of the system. In contrast to zone stopping, only a small portion of the sample zone is halted with zone trapping, leading to these beneficial effects.